Biology Chapter on Osmosis and Cell Membranes

Compound Light Microscope

• Eyepiece: Magnifies the image
• Coarse Adjustment Knob: Moves the stage up and down for initial focus (used with lowest power objective lens)
• Fine Adjustment Knob: Makes fine adjustments to the image for sharper focus (use with any objective lens, primarily medium and high power)
• Revolving Nosepiece: Holds the objective lenses and rotates them into position.
• Objective Lenses: Provide different magnification strengths.
• Stage: Supports the slide holding the specimen
• Stage Clips: Hold the slide firmly in place on the stage.
• Diaphragm: Regulates the amount of light passing through the specimen.
• Lamp: Provides light for viewing the specimen.
• Arm: Supports the microscope for carrying.
• Base: Provides a stable foundation.
• Mirror (if applicable): Reflects light onto the specimen instead of a lamp.

Trying Out A Microscope

• Procedure:
  • Place a slide on the stage.
  • Secure the slide with stage clips.
  • Position the lowest-power objective lens over the specimen .
  • Focus using the coarse adjustment knob.
  • If using the mirror instead of a lamp, be cautious to not allow direct sunlight to enter the microscope.
  • Adjust the fine adjustment knob to refine focus.

Cell Structures

• Cell Membrane: Thin outer layer that surrounds the cell.
• Cell Wall: Rigid outer layer surrounding plant cells.
• Cytoplasm: Liquid inside the cell.
• Nucleus: Large, centrally located structure (in both plant and animal cells).
• Vacuoles: Clear, liquid-filled spaces (in both plant and animal cells).

Comparing Plant and Animal Cells

• Similarities: Both contain cell membranes, cytoplasm, and a nucleus.
• Differences: Plant cells have a cell wall, chloroplasts, and a large central vacuole, which animal cells generally do not have.

Preparing Wet Mounts

• Materials: Slide, cover slip, a glass slide, eyedropper, tweezers (or toothpick), water and a small sample.
• Procedure:
  • Place a slide with a drop of water in front of you
  • Place the specimen on the water drop
  • Carefully place the cover slip over the specimen and gently lower it avoiding trapped air bubbles.

Testing Your Wet Mount

• Procedure:
  • Prepare a wet mount of a sample
  • Predict the appearance under low power.
  • Observe the slide and record predictions/observations.
  • Predict the appearance under medium and high power.
  • Adjust by slowly moving the slide and refocusing.
  • Record the observations in your notebook.

Viewing Plant and Animal Cells

• Different cell types and structures can be seen with a microscope, from the smallest to the largest components.
• Cell parts, such as the nucleus and mitochondria can be seen but others might require a higher power microscope to be observed.

Cells in Multicellular Organisms

• Cells are organized into tissues (e.g., muscle, nerve).
• Tissues combine to form organs (e.g., heart, brain).
• Organs function together in organ systems.

Cells Reproduce

• Multicellular/unicellular organisms reproduce to create more cells.
• Cell division is the process by which cells reproduce.
• Specialization of cells is important, as some cells or tissues are designed for specific tasks, such as blood transport (red blood cells) and organ function.

Tissues in Plants

• Plant cells are organized into three types of tissues:
  • Protective tissues
  • Photosynthetic/Storage tissues
  • Transport tissues

How Substances Move Into and Out of Cells

• Diffusion: Movement of particles from high concentration to low concentration
• Osmosis: Diffusion of water across a selectively permeable membrane.

Effects of Different Solutions on Cells

• Salt water (hypertonic solution) causes water to leave cells, shrinking them.
• Pure water (hypotonic solution) causes water to enter cells, swelling them.

Observing Unicellular Organisms

• Unicellular organisms can be observed and studied using a microscope.
• Prepare a wet mount of the organisms to observe them.
• Use the coarse and fine adjustment knobs carefully to view the specimen using different magnifications.
• Record your observations.

Common Unicellular Organisms

• Amoebas: use pseudopods to move and feed
• Paramecia: covered in cilia to move and feed